E. H. Kraus — Celestite- Bearing Rocks. 289 



namely, one part in 10,070 parts of water at 16*1°C. But, 

 inasmuch as the celestite usually occurs disseminated in lime- 

 stones, let us compare with the above figures concerning the 

 solubility of celestite, some showing the solubility of calcite. 

 Perhaps the most reliable are those of F. Kohlrausch and F. 

 Rose,* namely, that one part of calcite is soluble in 76,924 

 parts of water at 15° C. 



A comparison of these figures for the solubility of calcite 

 with the highest for celestite, which are by the same author- 

 ities — Kohlrausch and Rose — shows that celestite is more 

 than seven (7) times as soluble as the limestone rock in 

 which it usually occurs. But in this comparison we have con- 

 sidered the limestone to consist of pure calcium carbonate, 

 which is not the case. They are more or less dolomitic and 

 also contain some silica, thus their solubility would be even 

 less than that indicated for calcite. Of course, waters circu- 

 lating in nature are never pure, but contain oftentimes, among 

 other compounds in solution, varying amounts of carbon dioxide, 

 which increases to a very considerable extent the solubility of 

 the carbonate rocks. The porous character of these rocks, 

 however, shows conclusively that there is not enough of the 

 carbon dioxide in the percolating waters to cause the lime- 

 stones to dissolve more readily than the celestite. We can, 

 also, readily see that in order to account for the comparatively 

 easy solubility of celestite over the carbonate rocks, it is not at 

 all necessary to assume the presence of extraordinary amounts 

 of sodium, calcium, or magnesium chlorides in the circulating 

 water. 



Thus, by the continued action of water, the celestite dissemi- 

 nated in the strata near the surface, would pass into solution, 

 and as this descends the mineral may, under certain conditions, 

 be again deposited. In this way, the occurrence of celestite in 

 the cracks and cavities is to be explained. The same explana- 

 tion also applies to the " Crystal " cave. This cave, the ceiling 

 of which is perhaps 15 to 20 feet below the surface, is a large 

 cavity. Into this large cavity or cave, water containing celes- 

 tite in solution, which was obtained from the overlying strata, 

 flowed, and from it the large crystals crystallized. These large 

 and well-developed crystals indicate that crystallization took 

 place without any serious disturbance or interruption, there 

 being a continual addition of material, i. e., as fast as the celes- 

 tite was deposited more was brought in by the descending 

 water. Such occurrences of celestite — in the cracks and cavi- 

 ties — are of course of secondary origin. 



* Zeit. fur. physikal. Cheinie, xii, 162-166, 1893. 



